The present invention relates to a continuous process for the production of epoxylated addition polymers, to the polymeric products produced by the process, to powder and liquid coating applications containing the polymeric products made by the process, and to powder and liquid coatings containing epoxylated addition polymers.
Continuous processes for the production of polymers are well known in the art. However, many of the processes used to date to produce polymers for industrial use suffer from significant limitations including high cost, significant gelation problems when utilizing epoxy-containing monomers, poor incorporation levels of particular monomers, and an inability to produce polymers that can be utilized in weatherable and non-yellow coating applications.
U.S. Pat. No. 4,414,370, issued to Hamielec et al., discloses a continuous bulk polymerization process for polymerizing vinylic monomers to prepare low molecular weight polymers employing thermal initiation at reaction temperatures from 235xc2x0 C. to 310xc2x0 C. and residence times of at least 2 minutes in a continuous stirred reactor zone.
U.S. Pat. No. 4,529,787, issued to Schmidt et al., discloses a continuous bulk polymerization process including an initiator for preparing low molecular weight, uniform polymers from vinylic monomers at short residence times and moderate reaction temperatures to provide high yields of a product suitable for high solids applications.
U.S. Pat. No. 4,546,160, issued to Brand et al., discloses a continuous bulk polymerization process for polymerizing acrylic monomers to prepare low molecular weight, uniform, polymers for use in high solids applications which uses a minor amount of initiator at short residence times and moderate temperatures.
None of the prior art teaches how to overcome the problems related to producing epoxylated addition polymers at high temperatures using continuous processes. Typically, significant gel particle formation occurs when continuous, high temperature polymerization reactions are conducted to produce epoxylated addition polymers.
Moreover, epoxylated addition polymers are generally formed by the polymerization of epoxy-functional monomers together with methacrylate monomers and other selected monomers. Often the epoxy-functional monomers are themselves methacrylate monomers. Conventional high temperature polymerization methodologies have not been able to adequately solve problems encountered when producing such polymers which include low levels of incorporation of the methacrylate monomers into the final polymeric product. There remains a need for continuous high temperature polymerization processes to produce epoxylated addition polymers which overcome these shortcomings of such processes known in the art.
U.S. Pat. No. 5,256,452, issued to McMonigal et al., teaches the production of clear coatings using epoxylated polymers produced via a semi-batch process. These coatings, typically used for automobile finishes, can give a yellowish cast to the colored base coat which they cover. This is particularly a problem when the colored base coat is white. Unfortunately, clear coatings containing these epoxylated polymers produced according to U.S. Pat. No. 5,256,452 demonstrated excess yellowness when applied as either liquid or powder clear coatings over base coatings.
Finally, clear coatings containing the epoxylated polymers produced according to conventional processes have significant problems in addition to the yellowing problem described above. For example, clear coatings containing conventional epoxylated polymers also lack weatherability. When these conventional clear coatings are used in applications which expose them to extreme conditions, such as automobile coatings, they sometimes fail to provide the durability required. A need exists to produce epoxylated polymers for use in clear coatings that overcome the problems associated with conventional epoxylated polymers.
One object of the present invention is to provide a continuous, high temperature polymerization process for preparing a free radically polymerized epoxy-functional polymeric product, wherein the polymeric product is formed substantially free of gel particles. In one embodiment, this is accomplished in the present invention by continuously charging into a reactor at least one epoxy-functional acrylic monomer, and optionally at least one non-functional free radical polymerizable monomer(s), such monomers including, but not limited to, non-functional acrylate monomers, non-functional methacrylate monomers, non-functional styrenic monomers and combinations thereof. The reactor may also optionally be charged with at least one free radical polymerization initiator and/or one or more solvents. The reactor is maintained at an effective temperature for an effective period of time to cause polymerization of the monomers to produce a polymeric product from the monomers formed substantially free of gel particles within the reactor.
A further object of the present invention is to provide a continuous, high temperature polymerization process for preparing a free radically polymerized epoxy-functional polymeric product. The process comprises continuously charging into a reactor about 1% to 100% by weight based on the total weight of the monomers of at least one epoxy-functional acrylic monomer; optionally up to about 99% by weight based on the total weight of the monomers of one or more non-functional free radical polymerizable monomers, such monomers including, but not limited to, non-functional acrylate monomers, non-functional methacrylate monomers, non-functional styrenic monomers and combinations thereof, based on the total weight of the monomers; optionally at least one free radical polymerization initiator; and 0% to about 40% by weight.
Another object of the present invention is to provide a continuous, high temperature polymerization process for preparing a free radically polymerized epoxy-functional polymeric product. The process comprises continuously charging into a reactor about 15% to about 60% by weight of at least one epoxy-functional acrylic monomer based on the total weight of the monomers; up to about 85% by weight of at least one non-functional acrylate and/or nonfunctional methacrylate monomer based on the total weight of the monomers; about 0.0005 to about 0.06 moles of at least one free radical polymerization initiator per mole of monomers; 0% to about 25% by weight of at least one non-functional styrenic monomer based on the total weight of the monomers; and 0% to about 15% by weight of solvent based on the total weight of the monomers.
It is a further object of the present invention to provide a continuous, high temperature polymerization process for preparing a free radically polymerized epoxy-functional polymeric product that incorporates high levels of both epoxy-functional and non-functional methacrylate monomers into the polymeric product. In a preferred embodiment, the invention allows for of at least 60% by weight of the methacrylate monomers fed into the reactor to be converted into the epoxy-functional polymeric product. This is accomplished by continuously charging into a reactor at least one epoxy-functional acrylic monomer, at least one non-functional methacrylate monomer, at least one non-functional acrylate monomer, and optionally at least one free radical polymerization initiator. An effective temperature is maintained in the reactor for an effective period of time to cause polymerization of the monomers and produce a polymeric product. In some preferred processes, the acrylate monomer has a Tg of less than or equal to 30xc2x0 C., while in other processes, the acrylate monomer has a Tg of greater than 30xc2x0 C. In a preferred process, the acrylate monomer is cyclohexyl acrylate, and in still another preferred embodiment is isobornyl acrylate. In other preferred processes, the reactor is additionally continuously charged with at least one non-functional styrenic monomer or other non-functional free radical polymerizable monomers.
It is also an object of the present invention to maximize the conversion of all monomers in the reactor feed into the polymeric product of the present invention. This is done according to the present invention by adjusting the quantity of the non-functional acrylate monomer in the reactor feed.
Another object of the present invention is to provide a continuous, high temperature polymerization process for preparing a free radically polymerized epoxy-functional polymeric product. The process comprises continuously charging into a reactor about 15% to about 60% by weight at least one epoxy-functional acrylic monomer based on the total weight of the monomers, up to about 85% by weight of at least one non-functional methacrylate monomer based on the total weight of the monomers, 0% to about 25% by weight of at least one non-functional acrylate monomer based on the total weight of the monomers, about 0.0005 to about 0.06 moles of at least one free radical polymerization initiator per mole of monomers, 0% to about 25% by weight of at least one non-functional styrenic monomer based on the total weight of the monomers, and 0% to about 15% by weight of solvent based on the total weight of the monomers.
A further object of the present invention is to produce liquid and powder clear and pigmented coatings incorporating polymeric products of the present invention. These coatings exhibit enhanced properties such as lower yellowness when used in a clear coating, and/or enhanced weatherability when used in a clear or pigmented coating, when compared to similar coatings that comprise either comparable batch polymeric products and/or comparable acrylate free polymeric products.
Still another object of the present invention is to produce a powder coating composition comprising a polymeric product consisting essentially of about 1% to 100% by weight at least one epoxy-functional acrylic monomer based on the total weight of the monomers, optionally up to 99% by weight of at least one non-functional free radical polymerizable monomer, such monomers including, but not limited to, non-functional acrylate monomers, non-functional methacrylate monomers, non-functional styrenic monomers and combinations thereof, based on the total weight of the monomers, such that the monomers are polymerized into the polymeric product. The polymeric product in one embodiment comprises a monomer content of epoxy-functional acrylic monomer(s) of at least about 40%. The powder coating also comprises other materials sufficient to form a powder coating when combined with the polymeric product. The powder coating composition exhibits a Delta b value of 1.2 or less at standard conditions, more preferably, exhibiting a Delta b value of 1.05 or less at standard conditions, when the powder coating is a clear coating.
The invention also relates to a powder coating composition comprising a polymeric product consisting essentially of about 15% to about 60% by weight at least one epoxy-functional acrylic monomer based on the total weight of the monomers, up to 85% by weight of at least one non-functional acrylate and/or non-functional methacrylate monomer based on the total weight of the monomers, such that the monomers are polymerized into the polymeric product. The polymeric product in one embodiment comprises a monomer content of epoxy-functional acrylic monomer(s) of at least about 40%. The powder coating also comprises other materials sufficient to form a powder coating when combined with the polymeric product. The powder coating composition exhibits a Delta b value of 1.2 or less at standard conditions, more preferably, exhibiting a Delta b value of 1.05 or less at standard conditions, when the powder coating is a clear coating.
Other preferred powder coatings according to the present invention comprise a polymeric product which consists essentially of about 15% to about 60% by weight at least one epoxy-functional acrylic monomer based on the total weight of the monomers, up to 60% by weight of at least one non-functional methacrylate monomer based on the total weight of the monomers, up to 25% by weight of at least one non-functional acrylate monomer, such that the monomers are polymerized into the polymeric product. The polymeric product in one embodiment comprises a monomer content of epoxy-functional acrylic monomer(s) of at least about 40%. The powder coating composition further comprises other materials sufficient to form a powder coating. The powder coating composition exhibits a Delta b value of 1.2 or less at standard conditions, more preferably exhibiting a Delta b value of 1.05 or less at standard conditions, when the powder coating is a clear coating.
A further object of the present invention is a liquid coating composition comprising a polymeric product consisting essentially of about 1% to about 100% by weight at least one epoxy-functional acrylic monomer based on the total weight of the monomers, optionally up to 99% by weight of at least one non-functional free radical polymerizable monomer, such monomers including, but not limited to, non-functional acrylate monomers, non-functional methacrylate monomers, non-functional styrenic monomers and combinations thereof, based on the total weight of the monomers, such that the monomers are polymerized into the polymeric product. The polymeric product is mixed with other materials sufficient to form a liquid coating. The liquid coating composition exhibits a Delta b value of 1.2 or less at standard conditions, when the liquid coating is a clear coating.
A further object of the present invention is to produce a liquid coating composition comprising a polymeric product consisting essentially of about 15% to about 60% by weight at least one epoxy-functional acrylic monomer based on the total weight of the monomers, up to 85% by weight of at least one non-functional acrylate and/or non-functional methacrylate monomers based on the total weight of the monomers, such that the monomers are polymerized into the polymeric product. The polymeric product is mixed with other materials sufficient to form the liquid coating. The liquid coating composition exhibits a Delta b value of 1.2 or less at standard conditions, when the liquid coating is a clear coating.
These and other objects of the invention will be apparent from the specification that follows together with the appended claims.